The invention in its broad aspects relates to aza analogs of carboxyalkyl dipeptides derivatives which are useful as converting enzyme inhibitors and as antihypertensives. The compounds of this invention are represented by the following general formula: ##STR2## wherein: R and R.sub.3 are independently hydrogen, loweralkyl, loweralkenyl, loweralkynyl, aralkyl;
R.sub.1 is aralkyl, heterocycloalkyl, substituted aralkyl and substituted heterocycloalkyl wherein the substituents in the aryl and heterocyclo groups can each independently be amino, halo, aminoloweralkyl, hydroxy, loweralkoxy, loweralkyl, loweralkenyl, and loweralkynyl; loweralkyl substituted by amino, acylamino, heteroarylamino, aryloxy, heterocyclooxy, arylthio, heterocyclothio, hydroxyl; PA0 R.sub.2 is hydrogen, loweralkyl, loweralkenyl, loweralkynyl, amino loweralkyl, amino loweralkenyl, aminoloweralkynyl, aralkyl; PA0 A is hydrogen, cycloalkyl of 5-7 carbon atoms, aryl, heterocyclo; PA0 B is hydrogen, loweralkyl, loweralkenyl, loweralkynyl; or, PA0 A and B can be joined together to form ring structures which include N-CHCO.sub.2 R.sub.3 and which have the formulae: ##STR3## wherein: R.sub.3 is as defined above; PA0 Q.sub.1 and Q.sub.2, taken together, are CH.sub.2 CH.sub.2, CH.sub.2 --S, CHR.sub.4 S, CH.sub.2 --CH--OR.sub.5 wherein R.sub.4 is aryl or aryl substituted by hydroxyl, amino loweralkyl, loweralkenyl, loweralkynyl, amino, halo or alkoxy; and, R.sub.5 is hydrogen, loweralkyl, loweralkenyl, loweralkynyl, aryl, aralkyl, or CONR.sub.6 R.sub.7 wherein R.sub.6 and R.sub.7 can each independently be hydrogen, loweralkyl, loweralkenyl, loweralkynyl, aralkyl; PA0 W is a bond, CH.sub.2 ; PA0 Y is a bond, CH.sub.2, CH.sub.2 CH.sub.2 ; and, PA0 R and R.sub.3 are independently hydrogen, loweralkyl, loweralkenyl, loweralkynyl, aralkyl; PA0 R.sub.1 is aralkyl and heterocycloalkyl wherein the alkyl groups contain 1-4 carbon atoms; substituted aralkyl, and substituted heterocycloalkyl wherein the alkyl groups contain 1-4 carbon atoms and the substituents are halo, amino, amino loweralkyl, hydroxy; substituted alkyl of 1-6 carbon atoms wherein the substituent is amino, arylamino, aryloxy, alkylthio, arylthio, heterocyclothio, or hydroxy; PA0 R.sub.2 is hydrogen, loweralkyl, amino loweralkyl; PA0 A is cycloalkyl of 5-7 carbon atoms; PA0 B is hydrogen; or, PA0 A and B can be joined together to form ring structures which include NCHCO.sub.2 R.sub.3 and which have the formula: ##STR4## wherein: R.sub.3 is as defined above; PA0 Q.sub.1 and Q.sub.2, taken together, are CH.sub.2 CH.sub.2 CH.sub.2 S, CHR.sub.4 S, CH.sub.2 CH--OR.sub.5 wherein R.sub.4 is aryl or aryl substituted by hydroxyl; and, R.sub.5 is lower alkyl, aralkyl. PA0 R and R.sub.3 are independently hydrogen, loweralkyl, aralkyl; PA0 R.sub.1 is aralkyl and heterocycloalkyl wherein the alkyl groups contain 1-4 carbon atoms; substituted aralkyl and substituted heterocycloalkyl wherein the alkyl groups contain 1-4 carbon atoms and the substituents are halo or hydroxy; substituted alkyl of 1-6 carbon atoms wherein the substituent is aryloxy or arylthio; PA0 R.sub.2 is hydrogen, loweralkyl, amino loweralkyl; PA0 A and B can be joined together to form ring structures which include NCH--CO.sub.2 R.sub.3 and which have the formula: ##STR5## wherein: R.sub.3 is as defined above; PA0 Q.sub.1 and Q.sub.2, taken together, are CH.sub.2 CH.sub.2, CH.sub.2 S, CHR.sub.4 S, CH.sub.2 CH--OR.sub.5 wherein R.sub.4 is aryl or aryl substituted by hydroxyl; and R.sub.5 is loweralkyl. PA0 R is hydrogen, loweralkyl; PA0 R.sub.1 is aralkyl and heterocylcoalkyl wherein the alkyl groups contain 1-3 carbon atoms; substituted aralkyl wherein the alkyl groups contain 1-3 carbon atoms and the substituents are halo or hydroxy; substituted alkyl of 1-6 carbon atoms wherein the substituent is aryloxy or arylthio; PA0 R.sub.2 is hydrogen, methyl, 4-aminobutyl; PA0 R.sub.3 is hydrogen; PA0 A and B can be joined together to form ring structures which include NCHCO.sub.2 R.sub.3 and which have the formula: ##STR6## wherein R.sub.3 is as defined above, and which are proline, thiaproline, or 4--carboxy2--(2--hydroxyphenyl)thiazolidine.
the pharmaceutically acceptable salts thereof.
Preferred are compounds of Formula I wherein:
More preferred are compounds of Formula I wherein:
Most preferred are compounds of Formula I wherein:
The preferred, more preferred and most preferred compounds also include the pharmaceutically acceptable salts thereof.
The loweralkyl groups, except where noted otherwise, represented by any of the variables include straight and branched chain hydrocarbon radicals of from one to eight carbon atoms, for example, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, pentyl, isopentyl, hexyl, and the like. Loweralkenyl and loweralkynyl denote alkyl groups as described above which are modified so that each contains a carbon to carbon double bond or triple bond, respectively such as vinyl, allyl, butenyl, hexynyl, and the like. The aralkyl groups represented by any of the above variables have, except where noted otherwise, from one to six carbon atoms in the alkyl portion thereof and include for example, benzyl, phenethyl, cinnamyl, and the like. Halo means chloro, bromo, iodo or fluoro. Aryl, where it appears in any of the radicals unless otherwise noted, represents phenyl, naphthyl or biphenyl. Heterocyclic groups, where they appear, have 5--6 ring atoms in the cyclic portion thereof and contain one or more N, O or S heteroatoms such as, for example, pyridyl, thienyl, furyl, indolyl, benzthienyl, imidazoyl and thiazolyl. Acyl refers to loweralknoyl and aroyl groups.
The products of Formula (I) and the preferred subgroups can be produced by one or more of the methods and subroutes depicted in the following Reaction Schemes wherein R, R.sub.1, R.sub.2, R.sub.3, A, B, W, and Y are as defined above unless stated otherwise: ##STR7## As depicted in Reaction Scheme I, the aza analog compounds of the invention are generally produced by reacting the t-butyl ester of an imino acid II (A.noteq.H) with phosgene in the presence of triethyl amine in methylene chloride to obtain N-chlorocarbonyl derivative III. This intermediate III, in the presence of triethyl amine in methylene chloride, can then be reacted, for example, with isopropyl or N-isopropyl-N'-carbobenzyloxy hydrazine [prepared according to known methods such as that described by C. J. Gray, et al, Tetrahedron, 33, 837-40(1977)] to obtain, for example by isolation, filtration and condensation, protected intermediate IV. Hydrogen, in the presence of a 10% palladium-carbon catalyst in ethanol, is reacted with IV to afford deprotected intermediate derivative V. Alternatively, III can be reacted with a substituted hydrazine in the presence of triethylamine in methylene chloride to afford V. When t-butyl esters of amino acids II (A.dbd.H) are employed, phosgene can be replaced with carbonyldiimidazole to obtain an acylimidazole intermediate which reacts as described above for the N-chlorocarbonyl derivative III. Derivative V is dissolved in tetrahydrofuran (THF) and reacted with .alpha.-keto ester or acid VI to yield an .alpha.-keto ester-carbazone VII which, after treatment with sodium cyanoborohydride in ethanol, affords the .alpha.-aza-t-butyl ester peptide derivative VIII. Peptide derivative VIII is reacted with trifluoroacetic acid (TFA) to remove the t-butyl ester group yielding VIIIa. R.sub.3, when it is not hydrogen, can be introduced using R.sub.3 X (X=bromo, iodo) and a base such as cesium hydroxide. Removal of protecting groups, if present, then affords compounds of Formula I. Bis-esters of I can be obtained by Fisher esterification, for example, by treating Formula I compounds in an alcohol with dry HCl at room temperature.
Alternatively, compounds of Formula I when R.sub.2 =H can be obtained as shown in Reaction Scheme II. This procedure involves the synthesis of .alpha.-hydrazino acids or esters X followed by their condensation with N-chlorocarbonyl intermediates III. Subsequent esterification, if desired, and removal of protecting groups under standard conditions affords compounds of Formula I (R.sub.2 =H).
As will be evident to those skilled in the art and as demonstrated in the Examples which follow, reactive groups not involved in the condensations, such as amino, carboxy, hydroxyl, etc., may be protected by methods standard in peptide chemistry prior to the coupling reactions and subsequently deprotected to obtain the desired products.
Reactive group protection which can be employed during coupling reactions encompass known techniques such as, for example, by N-formyl, N-t-butoxycarbonyl, N-carbobenzyloxy, and 0-benzyl groups followed by their removal to yield (I). Furthermore, the R and R.sub.3 functions may include removable ester groups such as benzyl, ethyl, or t-butyl.
The starting materials required for the processes of the invention are known in the literature or can be made by known methods from known starting materials.
The above described syntheses can utilize racemates or enantiomers as starting materials. When diastereomeric products result from the synthetic procedures, the diastereomeric products can be separated by chromatographic or fractional crystallization methods. The resolution of intermediates or end products if desired can be accomplished by the crystallization of salts formed from optically active acids or bases.
Many of the compounds of this invention form salts with various inorganic and organic bases which are also within the scope of the invention. Such cationic salts include alkali metal salts like sodium and potassium salts, alkaline earth metal salts like the calcium and magnesium salts, salts with organic bases e.g., dicyclohexylamine salts, N-methyl-D-glucamine, salts with amino acids like arginine, lysine and the like. Those products which contain a basic function in R.sub.1 or R.sub.2 also afford salts with organic and inorganic acids such s maleic acid, hydrochloric acid, and the like. The non-toxic physiologically acceptable salts are preferred, although other salts are also useful, e.g., in isolating or purifying the product.
The salts may be formed by conventional means, as by reacting the free acid or free base forms of the product with one or more equivalents of the appropriate base or acid in a solvent or medium in which the salt is insoluble, or in a solvent such as water which is then removed in vacuo or by freeze-drying or by exchanging the cations of an existing salt for another cation on a suitable ion exchange resin.
The compounds of this invention inhibit angiotensin converting enzyme and thus block conversion of the decapeptide angiotensin I to angiotensin II. Angiotensin II is a potent pressor substance. Thus blood-pressure lowering can result from inhibition of its biosynthesis especially in animals and humans whose hypertension is angiotensin II related. Furthermore, converting enzyme degrades the vasodepressor substance, bradykinin. Therefore, inhibitors of angiotensin converting enzyme may lower blood-pressure also by potentiation of bradykinin. Although the relative importance of these and other possible mechanisms remains to be established, inhibitors of angiotensin converting enzyme are effective antihypertensive agents in a variety of animal models and are useful clinically, for example, in many human patients with renovascular, malignant and essential hypertension. See, for example, D. W. Cushman et al., Biochemistry 16, 5484 (1977).
The evaluation of converting enzyme inhibitors is guided by in vitro enzyme inhibition assays. For example, a useful method is that of Y. Piquilloud, A. Reinharz and M. Roth, Biochem. Biophys. Acta, 206, 136 (1970) in which the hydrolysis of carbobenzyloxyphenylalanylhistidinylleucine is measured. In vivo evaluations may be made, for example, in normotensive rats challenged with angiotensin I by the technique of J. R. Weeks and J. A. Jones, Proc. Soc. Exp. Biol. Med., 104, 646 (1960) or in a high renin rat model such as that of S. Koletsky et al., Proc. Soc. Exp. Biol. Med., 125, 96 (1967).
Thus, the compounds of this invention are useful as antihypertensives in treating hypertensive mammals, including humans, and they can be utilized to achieve the reduction of blood pressure by formulating in compositions such as tablets, capsules or elixirs for oral administration or in sterile solutions or suspensions for parenteral administration. The compounds of this invention can be adminis-tered to patients (animals and human) in need of such treatment in dosages that will at least provide pharmaceutical effectiveness. Although the dose will vary depending on severity of disease, weight of patient and other factors which a person skilled in the art will recognize, the dosage range will generally be about 0.5 to 50 mg per kilo per day.
This dose range can be adjusted on a unit basis as necessary to permit divided daily dosage. Naturally, the dose will vary depending on the severity of the disease, concurrent medication and other factors which a person skilled in the art will recognize.
Also, the compounds of this invention may be given in combination with diuretics or other antihypertensives. Typically these are combinations whose individual per day dosages range from one fifth of the minimally recommended clinical dosages to the maximum recommended levels for the entities when they are given singly. To illustrate these combinations, one of the antihypertensives of this invention effective clinically in the range 5-500 milligrams per day can be effectively combined at levels ranging from 1-500 milligrams per day with the following antihypertensives and diuretics in dose ranges per day as indicated:
hydrochlorothiazide (10-200 mg), timolol (5-60 mg), methyl dopa (65-2000 mg), the pivaloyloxyethyl ester of methyl dopa (30-1000 mg), indacrinone and variable ratios of its enantiomers (25-150 mg) and (-)-4-{3-{-[2-( -hydroxycyclohexyl)ethyl]-4-oxo-2-thiazolidinyl}propyl}benzoic acid (10-100 mg).
In addition, the triple drug combinations of hydrochlorothiazide (15-200 mg) plus amiloride (5-20 mg) plus converting enzyme inhibitor of this invention (1-500 mg) or hydrochlorothiazide (15-200 mg) plus timolol (5-50 mg) plus the converting enzyme inhibitor of this invention (1-500 mg) are effective combinations to control blood pressure in hypertensive patients.
The above dose ranges will be adjusted on a unit basis as necessary to permit divided daily dosage. Also, the dose will vary depending on the severity of the disease, weight of patient and other factors which a person skilled in the art will recognize.
Typically, the compounds of this invention can be formulated into pharmaceutical compositions as described below.
About 5 to 500 mg. of a compound or compounds of Formula I or a physiologically acceptable salt is compounded with a physiologically acceptable vehicle, carrier, excipient, binder, preservative, stabilizer, flavor, etc., in a unit dosage form as called for by accepted pharmaceutical practice. The amount of active substance in these compositions or preparations is such that a suitable dosage in the range indicated is obtained.
Illustrative of the adjuvants which may be incorporated in tablets, capsules and the like are the following: a binder such as gum tragacanth, acacia, corn starch or gelatin; an excipient such as microcrystalline cellulose; a disintegrating agent such as corn starch, pregelatinized starch, alginic acid and the like; a lubricant such as magnesium stearate; a sweetening agent such as sucrose, lactose or saccharin; a flavoring agent such as peppermint, oil of wintergreen or cherry. When the dosage unit form is a capsule, it may contain in addition to materials of the above type, a liquid carrier such as fatty oil. Various other materials may be present as coatings or to otherwise modify the physical form of the dosage unit. For instance, tablets may be coated with shellac, sugar or both. A syrup or elixir may contain the active compound, sucrose as a sweetening agent, methyl and propyl parabens as preservatives, a dye and a flavoring such as cherry or orange flavor.
Sterile compositions for injection can be formulated according to conventional pharmaceutical practice by dissolving or suspending the active substance in a vehicle such as water for injection, a naturally occurring vegetable oil like sesame oil, coconut oil, peanut oil, cottonseed oil, etc. or a synthetic fatty vehicle like ethyl oleate or the like. Buffers, preservatives, antioxidants and the like can be incorporated as required.
The following examples are illustrative of the invention and constitute especially preferred embodiments. The preferred diastereomers of these examples, which are at both carbon atoms bearing R.sub.1 and CO.sub.2 R.sub.3 of the natural L-amino acid configuration, are isolated by column chromatography or fractional crystallization. In most cases, these preferred absolute configurations can also be disignated (S)-.
In the following Examples, NMR chemical shifts are reported in ppm downfield from tetramethyl silane as internal standard. Optical rotations were measured in methanol solution.